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A Land Divided

By Amy Hardberger

October 2018

Just as humans require food and shelter, animals require habitat for survival.  Habitat includes the area needed to eat, drink and procreate. Without appropriate habitat, a species cannot survive.  While the impacts of habitat destruction are well understood, fragmentation – or breaking up – of habitat can be just as detrimental.  Because the land area has been interrupted, animals cannot easily move from one part to another leaving them on an island that can be insufficient for survival.  

Habitat fragmentation is one of the primary causes of biodiversity decline across the world.  In addition to separating animals from critical resources such as food and breeding grounds, animal groups can also be separated from one another.  

Fragmentation is caused by many things, but human development is the largest threat.  Road construction, increased traffic, pipelines, mining, and construction all contribute to this problem. Of these, roads have the most widespread and detrimental impact.  In addition to the physical removal of land from habitat for a new use, additional habitat may no longer be usable, due to increased light, noise, runoff, or pollution. Consideration of the entire footprint of a road is called ‘road ecology’.  In the United States, scientists estimate that the road system impacts the ecology of at least one-fifth of the country’s land area. In areas of the world with concentrated species, one road can have an outsized impact.  

Roads damage wildlife in four ways.  First, they decrease quantity and quality of habitat. Second, they increase mortality due to wildlife-vehicle collisions.  Third, roads prevent access to resources on the other side of the road and, finally, they subdivide wildlife populations into smaller and more vulnerable sub-populations. Habitat fragmentation can lead to extinction if a population's gene pool is sufficiently restricted.

As human population grows, the dangers of fragmentation and its impacts also increase.  It is critical that solutions be conceived and implemented during project development to minimize costs, avoid negative impacts, and allow people and nature to successfully coexist.  Of the solutions considered for road concerns, wildlife crossings are the most favored.

A Way Through 

A wildlife corridor is a semi-natural, linear passage that allows animals to safely move between historically connected habitats despite the addition of a human impediment, such as a road.  Wildlife corridors are not a new idea.  Fish ladders date back to at least the 17thcentury.  Many European countries have constructed methods for animal movement for several decades; however, rapidly growing populations have increased wildlife conflicts and thus, the demand for greater freedom of wildlife movement.  

Wildlife corridors can take many forms including underpass tunnels, viaducts, overpasses or bridges, strategic fence breaks, or culverts. These tools are often coupled with fencing to promote usage. The key to selecting a successful corridor is to tailor the solution to the animal species.  A corridor will not be successful if an animal will not, or cannot, make use of it.

A land bridge is an artificial wildlife corridor that provides a safe path for animals across a road.   While not required for all corridors, bridges can be essential for certain species that are unlikely, or unable, to cross in a subterraneous alternative (prey animals, like the endangered Grevy's zebra, for instance, will not use a tunnel, elephants are unlikely to pass through an underpass, and a tunnel could not accommodate a giraffe). Overpasses have been successful in Kenya south of Lewa, allowing the animals to migrate between the conservancy and Mt. Kenya.  Land bridges are also often a better alternative because they keep animals, particularly large mammals, off the roadway reducing danger to drivers - even more important at night when large dark animals cannot be seen until impact is imminent.

In addition to conservation concerns, wildlife-vehicle collisions have a significant cost for human populations.  Collisions with wildlife damage property and injure or kill passengers and drivers.  In Europe, it is estimated that number of collisions with large mammals is approximately 507,000 per year, resulting in 300 people killed, 30,000 injured, and property damage exceeding $1 billion. In the U.S., 1.5 million traffic accidents involving deer cause an estimated $1.1 billion in vehicle damage each year. Wildlife-vehicle collisions in the United States result in 29,000 injuries and more than 200 fatalities per year. 

In Kenya, similar road projects like the road from Isiolo to Moyale have shown significant road kill of species, particularly at night in certain sections.  This is not unusual as tarmac roads often increase vehicular night travel when many animals have peak movement.  Animals including aardwolves, hyenas, foxes, eagles and lions have been reportedly killed on the road. 
The imminent paving of the Rumuruti-Mararal Highway that bisects Mugie Conservancy will bring increased traffic, traveling at dangerous speeds, and it is critical that we do what we can to minimize the negative impact this has on wildlife.

What Does This Have To Do With Saving Cheetahs?

In July 2015, Mugie Conservancy, in partnership with KWS Institute of Zoology, collared one male cheetah that lives in a coalition brotherhood, to track their movements.  Over 798 days, the cheetah crossed the road 234 times, consistently in four locations, demonstrating the importance of access to all parts of the conservancy. These crossing locations are consistent with the movement of other animal species, shown through qualitative data collected through animal sightings and tracks.  The Institute recommended that an overpass be placed at two of the crossing locations and speed bumps and underpasses are recommended for others.

The cheetah's collar is no-longer working. An absolute necessity for the protection of the cheetah, both to monitor the movement for the road, but also to mitigate the human-wildlife conflict by warning herders when the cheetah are close to their stock. Information gathered about the cheetah movements and behavior can be used to deepen awareness and understanding and avoid the senseless, retaliatory killing of these precious animals (of which only 7,000 remain in the wild). You can contribute to our fundraising efforts to replace the collar with a donation to The Moyo Foundation.

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